Redox catalysts for the oxidative cracking of hydrocarbons, methods of making, and methods of use thereof

Abstract

A variety of redox catalysts, methods of making, and methods of using thereof are provided. Surface modified redox catalysts are provided having an oxygen carrier core with an outer surface that has been modified to enhance the selectivity of the redox catalyst for oxidative dehydrogenation. The surface modification can include forming a redox catalyst outer layer on the outer surface and/or suppressing sites that form nonselective electrophilic oxygen sites on the outer surface of the oxygen carrier. A variety of methods are provided for making the surface modified redox catalysts, e.g. modified Pechini methods. A variety of methods are provided for using the catalysts for oxidative cracking of light paraffins. Methods are provided for oxidative cracking of light paraffins by contacting the paraffin with a core-shell redox catalyst described herein to convert the paraffins to water and olefins, diolefins, or a combination thereof.

We claim: 
     
       1. A core-shell redox catalyst for cyclic redox based oxidative dehydrogenation or oxidative cracking of a paraffin comprising an oxygen carrier core of a perovskite having an outer shell,
 wherein
 (a) the perovskite comprises La 0.6 Sr 1.4 FeO 4  and the outer shell comprises LiFeO 2 ; 
 (b) the perovskite comprises Sr 3 Fe 2 O 7  and the outer shell comprises sodium tungstate; 
 (c) the perovskite comprises Sr 3 Fe 2 O 7  and the outer shell comprises LiFeO 2 ; or 
 (d) the perovskite comprises La 0.6 Sr 1.4 FeO 4  and the outer shell comprises sodium tungstate; 
 
 wherein the outer shell and the oxygen carrier are present at a molar ratio of about 0.5 to 2.5. 
 
     
     
       2. The redox catalyst of  claim 1 , wherein the redox catalyst is a nanoparticle having a diameter of about 50 nm to 500 nm. 
     
     
       3. The redox catalyst of  claim 1 , wherein the outer shell has an average thickness of about 10 nm or less. 
     
     
       4. The redox catalyst of  claim 1 , wherein the perovskite is La 0.6 Sr 1.4 FeO 4  and the outer shell is LiFeO 2 . 
     
     
       5. A method for oxidative cracking of paraffins, the method comprising:
 contacting the paraffins having from 2 to 7 carbon atoms with the redox catalyst according to  claim 1  under temperature of 600-800° C. to convert the paraffins to water and olefins, diolefins, or a combination thereof.